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Networks

1. What a network is
A Network is 2 or more devices connected together to share data, resources  and communication.

2. Why we network - 3 reasons

a. Communication
It allows us to quickly communicate with each other to find out information not on the network. E.g. social media, email, IM.

b. Share Resources
This allows us to share devices like printers without having to be directly linked into them. E.g. Printers

c. Share Data
This allows us to share files quickly and easily without having to transport them using a USB. E.g. pupil data

1. Topology - 6 different types - pros & cons

a. Peer to Peer
This is a type of Network that connects computers without a central server.

Pros
• No Network operating system needed.
• Doesn’t need an expensive server because individual workstations are used to access files.
• NO need for specialist staff because each user sets what they want to share.
• Much easier to set up than a client network.
• If one computer fails it won’t disrupt another part of the network. It just means some files are inaccessible for a bit.
Cons
• Because each computer can be accessed but other users it might slow down the computer of another user.
• Files and Folders cannot be centrally backed up
• Files might be difficult to find if the user doesn’t keep their files organised
• Virus protection is the responsibility of each user.
• There is little or no security apart from permissions.
B. Linear Bus
This is a type of network where all the parts are connected to a cable with terminators at each end. Easy to connect computers or resources
Peo • Uses less cable than a star network
Cons • If there is one break in the cable the whole network shuts down
• Terminators are required at both ends of the backbone cable.
• Difficult to identify the problem if the network breaks down
• Only useful for small areas
C. Star
Pros • Easy to install
• No disruptions when adding or removing devices
• Easy to detect faults and remove parts
Cons • Requires more cable than a linear topology
• If hub in the middle breaks the attached nodes are disabled
• More expensive because of hubs and cables.


D. Tree
Pros
• Point-to-point wiring for individual segments.
• Supported by several hardware and software venders.
Cons
• Overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks, the entire segment goes down.
• More difficult to configure and wire than other topologies.

E. Token Ring
Pros
• This type of network topology is very organized. Each node gets to send the data when it receives an empty token. This helps to reduces chances of collision. Also in ring topology all the traffic flows in only one direction at very high speed.
• Even when the load on the network increases, its performance is better than that of Bus topology.
• There is no need for network server to control the connectivity between workstations.
• Additional components do not affect the performance of network.
• Each computer has equal access to resources.
Cons
• Each packet of data must pass through all the computers between source and destination. This makes it slower than Star topology.
• If one workstation or port goes down, the entire network gets affected.
• Network is highly dependent on the wire which connects different components.
• MAU’s and network cards are expensive as compared to Ethernet cards and hubs.
F. Wireless
Pros
• Increased efficiency
• Better coverage
• Flexibility
• Cost savings
• New opportunities
Cons
• Wireless transmission is more vulnerable to attack by unauthorized users, so particular attention has to be paid to security
• You may suffer interference if others in the same building also use wireless technology or where other sources of radio signals are present.
• In some buildings getting consistent coverage can be difficult, leading to 'black spots' where no signal is available
• Wireless transmission can be slower and less efficient than 'wired' networks.



2. Devices
a. PC
This is the individual work station where a user can access the network
b. Server
This is a central point that is capable of accepting and executing requests of a client (a program). It shares resources to one or more clients.
c. Printer
This is a device that converts digital text and images to a hard copy. It prints them out.
d. Hub
This is an access point with multiple ports. When a data packet arrives at the hub it is copied and sent out to be accessed by the other computers attached to the hub.
e. Switch
This is a type of hub that directly sends the packet to the right address by reading the address on the packet.
f. Router
This is a device that forwards data packets along networks. They are located at gateways where two networks connect.
g. Patch panel
A panel of network ports contained together, usually within a telecommunications closet, that connects incoming and outgoing lines of a LAN or other communication, electronic or electrical system.


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1. Bandwidth - amount of data, equates hose pipe
This is the amount of data that can be carried from one point to another in a given moment usually a second. This can be explained using a garden hose and a fire hose, the garden hose can carry less water per second than the fire hose and so this is like bandwidth as some connections can carry more data than others. Also like if you put too much water in a hose, too much data being attempted to be transferred at one time can cause loss of data.
2. Wireless vs Hardwired comparison
Hardwired Networks take longer and are more difficult to install as all computers on the network need cables running to and from Ethernet ports and needs hubs and a central server. However they are more secure, cannot have black spots where the connection cannot reach and are not susceptible to interferences from radio or weather. Wireless connection however take less time to set up and don’t need Ethernet cables leading to every computer. However the routers are more expensive and if the router fails the whole network could go down rather than just having one cable break and one or two computers go down.
3. Peer to Peer vs Client Server comparison
Peer to peer networks are fairly inexpensive and easy to install needing only one cable as a backbone connecting up to ten computers together. However if the backbone cable breaks then the whole network is down. It is also less secure as there is no central server which can determine who shares what information and to access files you only need the password to access the files. On a client server you can have better security that d3etermines who shares what and who can access what. It also means that you cannot access the network unless you have a valid username and password. Although they are more expensive and only useful if you have many people accessing the network.
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